This time it's personal … Melanie Phillips. Photograph: Sarah Lee for the Guardian

Whatever would Melanie Phillips have done without the left? It has been her life's work to fight this many-headed hydra, hacking away tirelessly at its trendy teaching methods and loose morals and kooky environmentalism. But more than that, the heroic Phillips story depends not just on her vilification by the left but on leftwingers' supposed fury that she was once one of them. A martyr needs something to renounce, after all.

Her rupture with the left is rich polemical territory, and Phillips has explored it before. But with the publication of her memoir – a first venture from her new epublishing company – this time it's personal, and compellingly so.

Phillips was an only child, and she walked on eggshells. Her adored mother, Mabel, had had a nervous breakdown in her teens and remained mentally fragile, with obsessive-compulsive tendencies: theirs was a claustrophobic relationship, with the young Melanie convinced that "it would destroy her if I ever made her upset", and that she must always be unimpeachably good.

The chapter on her early childhood opens in the third person, as if such trauma could only be observed at a safe distance: the writing is melodramatic, yet the dread feels real. We see an anxious child raised to think of life in apocalyptic terms, never more than one mistake away from the mother's descent into darkness. When Phillips describes Mabel's compulsive handwashing as a strategy to "make the world an orderly place under her control, to stop it from disintegrating", it's tempting to draw parallels with the daughter's lifelong mission against moral and social collapse.

Her father, meanwhile, is portrayed as a disappointment. Albert Phillips died without savings in a rented flat, his daughter writes bitterly, having failed to do what "most other" poor Jews did and escape the East End for suburbia. For that, she blames his staunch socialist belief that workers don't aspire to the boss class: he had "no hinterland of aspiration", despite sending her to private school.

But what she really can't forgive is his failure to intervene in her childhood relationship with her mother. He was physically present, but she feels he deserted her emotionally, sparking a lifelong concern about fatherlessness: had he made clear how unfair her mother's expectations were, she writes, he "could have freed me, allowing me to feel entitled to live". Instead she has struggled long and hard with the belief that: "As someone whose very life had caused my mother to be so unwell, I was really not entitled to exist." This Guardian Angel has serious demons.

It takes great bravery for a woman too often dismissed as emotional – the "Mad Mel" of unfair myth – to write like this, and risk handing her critics ammunition. It would be monstrous not to feel both respect for that courage and sympathy. Yet as a chronicle of her personal battles with the left, and its "aggression towards any dissent or challenge", this book is problematic.

It's her 16 years at the Guardian that give the book its title and heart, so it should be said that your reviewer was at primary school when Phillips joined the paper in 1977, and worked for her subsequent paper, the Observer, only after Phillips left. I claim no inside knowledge. Yet while there are some instances of what she takes to be shocking antisemitism – one colleague refers to the 1982 Israeli invasion of Lebanon as "your war", making her feel her Jewishness renders her somehow not properly British – there's a puzzle at the heart of the book. Why do these ruthlessly intolerant, totalitarian hatemongers keep trying to meet her halfway, as indeed she occasionally yearns to meet them?

Her pioneering years in news editing, struggling with toddlers at home and stroppy reporters at work, sound grim: when she starts writing about how parental separation harms children, divorced friends cool on her, and party invites dry up. Yet for all her vivid descriptions of a Guardian staff who denounce anyone failing to toe the left-wing line as "beyond the moral pale", somehow they keep promoting her.

What do they do, when she starts asking how the poor can afford video recorders? There's a personal spat with a mentor figure, but far from being excommunicated Phillips goes on to become a leader writer, articulating the paper's daily voice. Her editor Peter Preston seems oddly relaxed about her supposedly insufferable views, approving leaders "even when it was clear he didn't altogether agree". When she decides global warming is bunkum, they give her an environment supplement to edit.

Even Tony Blair responds to criticism by asking her in for a chat, and agreeing with almost everything she says about fatherlessness. If there ever was a leftwing conspiracy to crush her, it clearly couldn't organise the proverbial in a brewery. Yet that original, provocative mind still circles endlessly around one all-consuming question: why do people hate me so?

She thinks it's partly because she's Jewish, but also because she "became a lightning rod for the onslaught by the left against the foundations of western society". It's a breathtaking claim to make for her own significance, and one longs to reassure her that half the nation isn't kept awake nights plotting the downfall of civilisation. But she's so wedded to "saying the unsayable", as her new Melanie Phillips-branded merchandise has it, that she can't see how sayable it has become – what with governments echoing her views on families and phonics, public opinion lurching ever rightwards, and decades of her being employed to say it.

It's easy to poke fun, of course. But there's nothing funny about an anxious, overburdened little girl growing into a conflicted adult who still cannot bear to call herself rightwing, and who weeps when interviewed 19 years later about the paper she once felt was a substitute family. If it all feels painfully unresolved, it's hardly any wonder she has a love-hate relationship with the left. As she herself says, the terrifying but necessary process of breaking free from her suffocating life with Albert and Mabel was always "mirrored and indeed intimately wrapped up with" her rejection of their Labour politics. This was never just about ideology.

So her story is ultimately a reminder that politics is governed by deep emotions that even in the heat of battle deserve to be understood and respected. She'd probably scoff at such woolly liberalism. But I bet there's a tiny part of her that still believes in it.